This invention relates to an X-ray exposure apparatus for manufacturing devices such as microdevices by transferring a pattern from a reticle such as a mask to a substrate such as a wafer using X-rays as the exposure light.
Semiconductor exposure apparatus of a variety of forms are in use in order to manufacture microdevices such as IC and LSI devices. Such a semiconductor exposure apparatus has an exposure light source specific to the apparatus and is so adapted that a circuit pattern written on a mask or reticle is burned into a wafer, which has been coated with a photoresist, by light emitted from the exposure light source.
It is required that the exposure light source have a short wavelength in order to raise the scale of integration of the microdevices. An X-ray light source has been proposed and developed as one candidate for a short-wavelength exposure light source.
X-ray light sources well known in the art include one using a synchrotron ring and one (referred to as a xe2x80x9cpoint-source X-ray sourcexe2x80x9d below) in which a target substance is irradiated with laser-light pulses to generate a plasma, and the plasma is used to produce X-rays.
The synchrotron ring is advantageous in that the X-rays generated exhibit a high intensity. A disadvantage of the synchrotron ring is its large size. This apparatus is inefficient in terms of cost and installation space unless the apparatus is provided with 10 to 20 ports per light source and an exposure apparatus is connected to each port. The point-source X-ray source, on the other hand, generates X-rays of comparatively low intensity, bit is small in size and generally is used by connecting one exposure apparatus per light source.
Various X-ray generating mechanisms have also been proposed for the point-source X-ray source. All of the point-source X-ray sources are such that radial X-rays having a certain solid angle are emitted from the X-ray source. In order for the point-source X-ray source to be used for the exposure of microdevices, it is desired that the X-rays that are projected upon the mask and wafer be parallel. To achieve this, an implementation has been considered in which the X-rays emitted from the point-source X-ray source are introduced to the exposure apparatus upon having their angle of divergence reduced using an X-ray optics element referred to as a collimator.
FIG. 11 is a schematic view illustrating an example of the structure of an X-ray exposure apparatus having a point-source X-ray source according to the prior art. In the X-ray exposure apparatus shown in FIG. 11, X-rays emitted from a point-source X-ray source 901 at a certain solid angle are introduced into a collimator 902. The latter is designed in conformity with the solid angle of the X-rays introduced. X-rays output from the collimator 902 are introduced into an exposure unit 903. The design is such that the angle of all X-rays output from the collimator 903 will be approximately perpendicular to the surface direction of a mask within the exposure unit 903. An example of the structure of the collimator 903 is one in which a number of capillary tubes are shaped in accordance with the angle of the X-rays on the input and output sides and are bundled together. The exit of the point-source X-ray source 901, the collimator 902 and an X-ray window 906 are constructed in the form of a chamber in which a gas can be sealed. In order to suppress attenuation of the X-rays, highly pure helium gas is sealed within the chamber as the atmosphere and the interior of the chamber is held at atmospheric pressure or lower. Though FIG. 11 is an example by which the point-source X-ray source 901 and the collimator 902 are configured in an X-ray introduction chamber 905, several other examples of implementation are available.
X-rays are introduced into the exposure unit 903 from the X-ray introduction chamber 905 through the X-ray window 906. The latter is used as an X-ray introducing portion that serves also as a pressure partition if the pressure on the side of the X-ray introduction chamber 905 differs from that within the exposure unit 903. An example of the X-ray window 906 known in the art is a thin film obtained by forming beryllium to a thickness of several microns to several tens of microns. The exposure unit 903 is constructed to suppress attenuation of the X-rays, highly pure helium gas is sealed within the chamber of the exposure unit 903 as the atmosphere and the interior of the chamber is held at atmospheric pressure or lower. If the gas purity and pressure in the X-ray introduction chamber 905 are the same as those in the chamber of the exposure unit 903, the X-ray window 906 can be eliminated.
With regard to the exposure unit 903, a mask 904 is carried in and out by a mask transport device, which is not shown. The mask 904 is held by a mask chuck (not shown) in order that exposure may be performed.
A wafer 903 is carried in and out by a wafer transport device, which is not shown. The wafer 907 is held by a wafer chuck 909 mounted on a wafer stage 908 in order that exposure may be performed. The wafer stage 908 has a precision positioning mechanism for positioning an exposure area on the wafer 907 with respect to the mask 904.
X-rays introduced into the exposure unit 903 have their intensity measured by an X-ray sensor 910 outside the exposure area. On the basis of the measured X-ray intensity, the exposure unit 903 controls the X-ray source device in such a manner that the optimum amount of exposure will be obtained. For example, in the case of an X-ray source device that generates X-rays in a pulsed form, the amount of exposure is controlled by commanding the number of pulses generated and the intensity of each pulse.
However, in a case wherein the point-source X-ray source according to the prior art is such that one collimator is combined with one point-source X-ray source, a problem which arises is that a large part of the energy radiated from the light source is not utilized.
In FIG. 11, only area B is utilized in exposure; other areas A and C represent dead space. In order to facilitate an understanding of the concept, FIG. 11 is drawn in such a manner that all X-rays emanate from the X-ray emission point of the point-source X-ray source. In actuality, however, emission of unnecessary X-rays is undesirable and, therefore, X-rays are shielded in the point-source X-ray source or exterior thereto. In either case, it can be construed that the efficiency with which all of the radiated energy of the light source is utilized is poor owing to the placement of various devices.
In order to solve the foregoing problem, the area of the collimator opening should be enlarged relative to the X-rays that emanate from the point-source X-ray source. However, if is it attempted to merely enlarge the single collimator, an angular disparity with respect to the emission angle of the collimator will grow larger as the periphery of the collimator is approached. This makes designing the apparatus extremely difficult.
Accordingly, the present invention has been proposed to solve the foregoing problems of the prior art, and has as its object to provide an X-ray exposure apparatus in which the efficiency of utilization of all the radiant energy possessed by X-rays is raised over that of the prior art. The present invention adopts a creative approach wherein use is made of a plurality of collimators of a number that lend itself to actual design and one exposure unit is connected to each collimator.
Specifically, according to the present invention, the foregoing object is attained by providing an X-ray exposure apparatus comprising: an X-ray source for generating pulsed X-rays; first to nth exposure means which use X-rays emitted from the X-ray source, wherein the exposure means project patterns of first to nth masks onto respective ones of first to nth substrates that are to be exposed.
Here, xe2x80x9cnxe2x80x9d represents an integer of 2 or greater, but the upper limit on n is the maximum number of collimators that can be designed in view of structural limitations.
In a preferred embodiment, the X-ray exposure apparatus further comprises first to nth (where n represents an integer of 2 or greater) collimators for varying at least one of angle and intensity of X-rays generated by the X-ray source.
Thus, it is possible to provide and X-ray exposure apparatus having a plurality (n) of exposure units for manufacturing microdevices and the like, wherein efficient utilization of all the radiant energy possessed by X-rays emitted from a single point-source X-ray source is raised over that of the prior art.
In a preferred embodiment, the X-ray exposure apparatus further comprises first to nth shutters situated between the X-ray source and respective ones of the masks and having one, two or more shielding members for shielding X-rays that irradiate the masks, first to nth shutter drive units for driving respective ones of the shutters, and a shutter controller for controlling each of the shutters.
In a preferred embodiment, the shutter drive unit controls the first to nth shutters depending upon the state of the X-ray source and at least one state among the states of the first to nth exposure means.
In a preferred embodiment, timing of X-ray emission from the X-ray source is controlled by an X-ray emission trigger signal, the apparatus further comprising an X-ray emission trigger generating unit for generating the X-ray emission trigger signal depending upon the state of the X-ray source and at least one state among the states of the first to nth exposure means.
In a preferred embodiment, the intensity of X-rays from the X-ray source is controlled by an X-ray intensity control signal, the apparatus further comprising an X-ray intensity control signal generator for generating an X-ray intensity signal control signal depending upon the state of the X-ray source and at least one state among the states of the first to nth exposure means.
In a preferred embodiment, the X-ray exposure apparatus further comprises a total control unit, which receives information for specifying the internal status of a point-source X-ray source unit having the point-source X-ray source, as a status signal from the point-source X-ray source unit, for exercising total control, which combined the shutter control unit and a plurality of controllers that control the exposure states of each of the exposure means based upon measurement values from a plurality of sensors that measure the X-ray intensities of respective ones of the exposure means, wherein the total control unit sends the X-ray emission trigger signal generating unit a trigger generation command and sends the X-ray intensity control signal generator and an X-ray intensity value and/or X-ray intensity command.
In a preferred embodiment, the total control unit has means for controlling exposure timing of each exposure means in accordance with a prescribed objective, the exposure timing being tunable within a range of set values that have been set in the total control unit.
In a preferred embodiment, the X-ray exposure apparatus further comprises first to nth moving means for moving at least one of respective ones of the masks and the substrates.
In a preferred embodiment, an optical-axis center of each collimator is configured radially with respect to the X-ray source.
For example, laser light is condensed to irradiate a solid metal target with pulsed laser light, thereby plasmatizing the metal surface of the target to generate X-rays.
In any of the X-ray exposure apparatus mentioned above, the type of the X-ray source is not limited to one that generates pulsed X-rays, and X-ray sources other than those that produce pulsed X-rays can be applied to the X-ray exposure apparatus of the embodiment.
With regard to a change in intensity of the X-rays owing to each of the n collimators from the first to the nth collimator, the X-ray intensity distribution may be made uniform by the design of each collimator if the intensity distribution of the X-rays emitted from the X-ray source is non-uniform.
A method of manufacturing a semiconductor device according to the present invention comprises the steps of placing a plurality of semiconductor manufacturing apparatus, which includes the above-described X-ray exposure apparatus, in a plant for manufacturing semiconductors, and manufacturing a semiconductor device by the plurality of semiconductor manufacturing apparatus.
A semiconductor manufacturing plant according to the present invention comprises: a plurality of semiconductor manufacturing apparatus inclusive of the above-described X-ray exposure apparatus, a local-area network for interconnecting the plurality of semiconductor manufacturing apparatus, and a gateway for connecting the local-area network and an external network outside the plant, whereby information relating to at least one of the plurality of semiconductor manufacturing apparatus can be communicated by data communication.
A method of maintaining an X-ray exposure apparatus installed in a semiconductor manufacturing plant according to the present invention comprises the steps of providing a maintenance database, which is connected to an external network of the semiconductor manufacturing plant, by a vendor or user of the X-ray exposure apparatus, connecting the X-ray exposure apparatus to a local-area network within the semiconductor manufacturing plant, and maintaining the X-ray exposure apparatus, based upon information that is stored in the maintenance database, utilizing the external network and the local-area network.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.